The present invention relates to improvements in a method and in an apparatus for ascertaining the dimensions and positions of film frames on roll films. More particularly, the invention relates to improvements in a method and apparatus for automatically ascertaining the positions and dimensions of frames on roll films with photoelectronic monitoring means. Still more particularly, the invention relates to improvements in a method and apparatus for ascertaining the dimensions and positions of film frames as considered in the longitudinal direction of a single roll film but especially in the longitudinal direction of a strip or web of spliced-together (coherent) roll films which may but need not have frames of different sizes.
German Pat. No. 1,285,317 discloses an apparatus which is used to provide a marginal portion of each roll film with a series of indicia or markers in the form of notches or the like, one for each film frame, in order to facilitate proper positioning of the respective film frames in a copying machine for the making of prints from exposed and developed photographic films. The arrangement is such that the distance between the monitoring station (where the dimensions of the film frames are ascertained) and the marking or indicia applying station is somewhat less than the combined length of two film frames, as considered in the longitudinal direction of the roll film. This renders it possible to verify the determination of the dimension of a film frame following detection of the leading edge of such frame by the monitoring device or devices before the indicia applying apparatus is actuated to provide the marginal portion of the roll film with a notch denoting the position of the freshly monitored film frame. Thus, the interval which elapses for advancement of an increment of roll film from the monitoring station to the indicia applying or marking station is sufficiently long to enable the monitoring device to detect the trailing edge of the film frame whose leading edge has been detected during a given interval and/or to detect other information which can be evaluated to reliably ascertain the dimensions of the freshly detected frame and to thus ensure that the notch will be applied in an optimum position for adequate positioning of the respective film frame in the copying machine. Such other information can constitute detection of the leader of the next-following film frame so that an evaluating system can readily ascertain the length of a film frame by the simple expedient of determining the distance between the leaders of two successive frames minus the anticipated or customary width of a frame line between such frames.
Another method of ascertaining the length of successive film frames on a roll film or a strip or web consisting of several roll films is disclosed in commonly owned U.S. Pat. No. 4,167,678 to Mischo et al. This patent discloses a method of relying on a parameter which is indicative of the actual length of film frames in a given roll film, such reliance ensuring a more predictable and more accurate determination of locations for the application of notches which facilitate proper positioning of film frames in the copying machine. The distance between the monitoring or scanning station and the indicia applying station equals between five and six times the length of a film frame, as considered in the longitudinal direction of the monitored roll film. This ensures that the failure of monitoring means to detect the leading edge and/or the trailing edge of one or more film frames does not detract from reliability of the monitoring operation and of the application of notches in optimum positions for adequate positioning of the film frames in the copying machine. The same holds true if one or more frames are not detectable at all, e.g., due to failure to expose such frames prior to removal of a roll film from the camera. Detection of the remaining leading and/or trailing edges between the spaced-apart monitoring and indicia applying stations of the apparatus which is disclosed in the patent to Mischo et al. suffices to ensure predictable detection of the length of film frames and proper application of notches or other forms of indicia. The information which is gathered by the monitoring device while a length of roll film advances from the monitoring to the indicia applying station can be processed in a computer or by interpolation.
A drawback of each of the just described prior apparatus is that the apparatus must receive information pertaining to the actual length of film frames. In other words, the apparatus which are disclosed in the aforementioned patents can ensure proper positioning of notches or other types of indicia relative to the corresponding film frames only upon receipt of advance information pertaining to the actual length of film frames on roll films wnich are caused to pass through such apparatus. This is due to the fact that these apparatus must be set up to furnish scanning intervals not longer than that which is necessary to transport a film frame past the monitoring station.
Large-scale film processing laboratories presently treat exposed and developed films in the form of long strips or webs containing a substantial number of successive roll films which are spliced together end-to-end and often contain, or are likely to contain, roll films having frames of different sizes. Though the number of roll films with 24.times.36 film frames still prevails, the number of roll films having square film frames (24.times.24 mm) or so-called half formats (18.times.24 mm) is steadily on the increase. This renders it impossible to properly identify the frames on a web or strip consisting of several roll films with different film frames by resorting to the aforediscussed conventional monitoring and indicia applying apparatus. Advance determination of the dimensions of film frames on successive spliced-together roll films would be too cumbersone and practically impossible at speeds which are necessary in a modern processing laboratory.
German Pat. No. 1,953,014 discloses an apparatus which is capable of automatically detecting the formats of successive film frames. However, this apparatus is highly complex, sensitive and impractical because it necessitates the transport of strips of roll films therethrough in advance of the transport of such strips into a copying machine. In other words, each strip must be conveyed first through the patented apparatus and is thereupon introduced into the conveyor system which advances the film frames through the copying machine.